1. Field of the Invention
The present invention relates generally to the field of machinery for forming bells or sockets in one end of length of plastic pipe to permit joining adjacent lengths of plastic pipe in end to end juxtaposition by inserting the unbelled or spigot end of one lengths of plastic pipe into the bell or socket which is formed in the proximate end of the next adjacent length of pipe.
2. Description of the Prior Art
In prior art types of pipe belling equipment, it has been known to position a shaped mandrel of predetermined configuration and size within a belling machine and to serially advance discrete lengths of plastic pipe, each having one end preheated, into axial alignment with belling mandrel. Suitable operating mechanisms have been developed and have been utilized to either axially move the pipe onto and over the mandrel or alternately, to axially move the mandrel into the heated end of the pipe for pipe end shaping into the desired bell or hub-shaped configuration. In certain designs, the prior pipe belling operations have been conducted within a suitable environmental chamber whereby pressure could be introduced into the chamber and about the pipe to press the preheated, softened pipe walls uniformally against the outer periphery of the mandrel. In my co-pending application Ser. No. 635,803 entitled "Pressure Chamber", filed July 30, 1984, one such environmental chamber has been fully set forth.
In accordance with more recent popular practice, it has become increasingly important to provide an internal groove in the bell configuration when the bell or hub shape was formed to provide a convenient annular groove to seat therein a sealing gasket in a manner to facilitate the making up of a leak proof junction between adjacent lengths of pipe in a piping system. U.S. Pat. No. 4,238,180 entitled "Mandrel With Identical Expanding Segments" is exemplary of a belling mandrel which incorporates construction features suitable to apply a circular, internal groove in the hub configuration for receipt of a gasket therein when the bell or hub of the plastic pipe is being formed.
However, so far as is known to the present applicant, despite all of the efforts of the many prior workers in the field to improve the joining procedures and constructions when utilizing plastic pipes, the seating of a sealing gasket in the junction between the spigot end of one length of pipe and the hub end of the next adjacent length of pipe, either with or without a peripheral internal groove formed in the hub, has always required a separate, relatively time consuming operation to properly install and seat a sealing gasket in proper position to seal the pipe junction against leakage.